[Spice-devel] Usb redirection

Hans de Goede hdegoede at redhat.com
Tue Dec 11 23:19:06 PST 2012


On 12/12/2012 01:43 AM, Jackson wrote:
> whether the usb 2.0 is supported in usbredirection or not?


> and what is usb transmission speed depended on?

For bulk transfers (ie usb mass storage devices) mostly latency,
on my i5 workstation using loopback networking (so very low latency),
I can read natively from a cheap USB-thumbdrive at 18 MB/s where as
in a vm I get 13 MB/s. Note that I've been optimizing the latencies
in our ehci emulation lately, and the 13 MB/s is with my very latest
qemu code. For qemu-1.3 it is 11 MB/s and for qemu in RHEL-6 it is
8 MB/s.

For isochronous devices (webcams, audio) we use buffering to hide
the latency + jitter to both sides, so there the transmission speed
is (and must be) the same as using the usb device directly. Note that
this requires that you've enough bandwidth on the network. We cannot
magically make a 480Mbps webcam work on a 100Mbit network connection.

BTW the above all applies to the new native fully FOSS USB redirection,
not the old third-party proprietary USB redirection used in older
versions of RHEV.



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